Organic electroluminescence device emitting white light

ABSTRACT

An organic electroluminescence device emitting white light which emits white light and exhibits properties sufficient for practical applications, i.e., a high efficiency of light emission and a long life, is provided. The organic electroluminescence device emitting white light comprises a pair of electrodes and a layer of a light emitting medium disposed between the pair of electrodes, wherein the layer of a light emitting medium comprises a light emitting material emitting blue light and a fluorescent compound having at least one structure selected from a fluoranthene skeleton structure, a pentacene skeleton structure and a perylene skeleton structure.

TECHNICAL FIELD

The present invention relates to an organic electroluminescence device(hereinafter, electroluminescence will be referred to as EL) emittingwhile light and, more particularly, to an organic EL device having ahigh efficiency and a long life and emitting white light.

BACKGROUND ART

Electroluminescence devices which utilize electroluminescence show highself-distinguishability because of the self-emission and are excellentin impact resistance because they are completely solid devices.Therefore, electroluminescence devices have been attracting attentionfor application as light emitting devices in various types of displayapparatus.

The electroluminescence devices include inorganic electro-luminescencedevices in which an inorganic compound is used as the light emittingmaterial and organic electroluminescence devices in which an organiccompound is used as the light emitting material. Organicelectroluminescence devices have been extensively studied for practicalapplication as a light emitting device of the next generation becausethe applied voltage can be decreased to a large extent, the size of thedevice can be reduced easily, consumption of electric power is small,planar light emission is possible and three primary colors are easilyemitted.

As for the construction of the organic electroluminescence device, thebasic construction comprises an anode/an organic light emitting layer/acathode. Constructions having a hole injecting and transporting layer oran electron injecting layer suitably added to the basic construction areknown. Examples of such construction include the construction of ananode/a hole injecting and transporting layer/an organic light emittinglayer/a cathode and the construction of an anode/a hole injecting andtransporting layer/an organic light emitting layer/an electron injectinglayer/a cathode.

Recently, organic EL devices for display apparatuses have been developedactively. In particular, a device which can emit white light is themajor target of the development. An organic EL device emitting whitelight can be used as the light source for single color displays and backlight. Moreover, an organic EL device emitting white light can be usedfor full color display when color filters are attached to a displayapparatus.

For examples, an organic EL device emitting white light is disclosed inthe U.S. Pat. No. 5,503,910, in which a laminate of a light emittinglayer emitting blue light and a light emitting layer emitting greenlight is used as the layer of a light emitting medium and a fluorescentcompound emitting red light is added to the layer of a light emittingmedium. An organic EL device emitting white light is disclosed in theU.S. Pat. No. 5,683,828, which has a layer of a light emitting mediumobtained by adding a complex compound containing boron which is afluorescent compound emitting red light to a light emitting layeremitting bluish green light. An organic EL device emitting white lightis disclosed in Japanese Patent Application Laid-Open No. Heisei10(1998)-308278, which has a light emitting medium obtained by adding abenzothioxanthene derivative which is a fluorescent compound emittingred light to a light emitting layer emitting bluish green light.

However, the device disclosed in the U.S. Pat. No. 5,503,910 has anefficiency of light emission as low as about 1 lumen/W and a life asshort as about 1,000 hours although white light is emitted. The devicedisclosed in the U.S. Pat. No. 5,683,828 has an efficiency of lightemission as low as about 2.6 cd/A although white light is emitted. Thedevice disclosed in Japanese Patent Application Laid-Open No. Heisei10(1998)-308278 has an efficiency of light emission as low as about 1lumen/W although white light is emitted. No devices sufficiently satisfythe requirements for practical application with respect to theefficiency of light emission and the life.

DISCLOSURE OF THE INVENTION

The present invention has an object of providing an organic EL deviceemitting white light which emits white light and exhibits propertiessufficient for practical applications, i. e., a high efficiency of lightemission of 5 lumen/W or greater and 5 cd/A or greater and a long lifeof 10,000 hours or longer.

As the result of extensive studies by the present inventors to achievethe above object, it was found that, when the layer of a light emittingmedium comprises a light emitting material emitting blue light and afluorescent compound having at least one structure selected from thefluoranthene skeleton structure, the pentacene structure and theperylene structure, an organic EL device comprising this layer of alight emitting medium disposed between a pair of electrodes has a highefficiency of light emission and a long life and emits white light. Thepresent invention has been completed based on this knowledge.

The present invention provides an organic electroluminescence deviceemitting white light which comprises a pair of electrodes and a layer ofa light emitting medium disposed between the pair of electrodes, whereinthe layer of a light emitting medium comprises a light emitting materialemitting blue light and a fluorescent compound having at least onestructure selected from a fluoranthene skeleton structure, a pentaceneskeleton structure and a perylene skeleton structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an examples of the construction of the organic EL deviceemitting white light of the present invention.

FIG. 2 shows another examples of the construction of the organic ELdevice emitting white light of the present invention.

FIG. 3 shows another examples of the construction of the organic ELdevice emitting white light of the present invention.

FIG. 4 shows another examples of the construction of the organic ELdevice emitting white light of the present invention.

THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION

The organic EL device of the present invention has, as shown in FIG. 1,a construction comprising a pair of electrodes and a layer of a lightemitting medium disposed between the pair of electrodes.

The layer of a light emitting medium comprises a light emitting materialemitting blue light and a fluorescent compound having at least onestructure selected from the fluoranthene skeleton structure, thepentacene skeleton structure and the perylene skeleton structure.

The layer of a light emitting medium comprises organic compounds as themain components thereof and is a medium providing a field fortransportation and recombination of electrons and holes which areinjected from the electrodes. This layer may comprise a single layer ora plurality of layers. When the layer of a light emitting mediumcomprises a plurality of layers, the layers comprised in the layer of alight emitting medium include a hole injecting layer, a holetransporting layer, a light emitting layer and an electron transportinglayer.

In the present invention, various constructions of the layers can beused.

(1) In the first construction, similarly to the construction shown inFIG. 1, the layer of a light emitting medium comprises light emittinglayer A which comprises the light emitting material emitting blue lightand the fluorescent compound.

The layer of a light emitting medium may comprise a light emitting layeremitting blue light and light emitting layer A described above.

In this construction, the layer of a light emitting medium may compriselight emitting layer A and organic layers other than light emittinglayer A. For example, as shown in FIG. 2, light emitting layer A may belaminated with a charge transporting layer such as a hole injectinglayer, a hole transporting layer and an electron transporting layer. Thecharge transporting layer and light emitting layer A may be laminated inthe order reverse to that shown in FIG. 2. Layers other than the chargetransporting layers such as an electron barrier layer, a hole barrierlayer, an organic semiconductive layer, an inorganic semiconductivelayer and a layer for improvement of adhesion may also be contained inthe laminate.

It is preferable that light emitting layer A described above comprisesthe light emitting material emitting blue light and a fluorescent dopantemitting blue light and/or that the light emitting layer emitting bluelight comprises the light emitting material emitting blue light and afluorescent dopant emitting blue light.

(2) In the second construction, as shown in FIG. 3, the layer of a lightemitting medium comprises light emitting layer B comprising the lightemitting material emitting blue light and a layer comprising thefluorescent compound. The layer comprising the fluorescent compound andlight emitting layer B may be laminated in the order reverse to thatshown in FIG. 3. Charge transporting layers and other layers such as anelectron barrier layer, a hole barrier layer, an organic semiconductivelayer, an inorganic semiconductive layer and a layer for improvement ofadhesion may be disposed between the layer comprising the fluorescentcompound or light emitting layer B and the electrodes.

In this construction, it is preferable that light emitting layer B is alight emitting layer emitting blue light, the layer comprising thefluorescent compound is a light emitting layer which comprises a lightemitting material and the fluorescent compound and emits yellow, orangeor red light and the light emitting layer emitting blue light comprisesa light emitting material emitting blue light and a dopant emitting bluelight. As the light emitting material comprised in the layer comprisingthe fluorescent compound, a light emitting material emitting blue orgreen light is preferable.

(3) In the third construction, as shown in FIG. 4, the layer of lightemitting medium comprises a light emitting layer emitting blue light anda layer of the fluorescent compound. The layer of the fluorescentcompound and the light emitting layer emitting blue light may belaminated in the order reverse to that shown in FIG. 4. Chargetransporting layers and other layers such as an electron barrier layer,a hole barrier layer, an organic semiconductive layer, an inorganicsemiconductive layer and a layer for improvement of adhesion may bedisposed between the layer of the fluorescent compound or the lightemitting layer emitting blue light and the electrodes.

The layer of the fluorescent compound is a layer which contains 20 to100% by weight of the fluorescent compound and emits yellow, orange orred light. In the above construction, it is preferable that the lightemitting layer is a light emitting layer emitting blue light and thelayer of the fluorescent compound is a light emitting layer whichcomprises the fluorescent compound and emits yellow, orange or redlight. It is more preferable that the light emitting layer emitting bluelight comprises the light emitting material emitting blue light and afluorescent dopant emitting blue light. As the light emitting materialcomprised in the layer of the fluorescent compound, a light emittingmaterial emitting blue or green light is preferable.

As described above, in the first to third constructions, light emittinglayer A, light emitting layer B and the light emitting layer emittingblue light may comprise the light emitting material emitting blue lightand the fluorescent dopant emitting blue light so that the property toemit blue light is enhanced. The fluorescent dopant emitting blue lightis a compound which is added to enhance the property of the lightemitting layer. Preferable examples of the fluorescent dopant emittingblue light include styrylamines, styryl compounds substituted with anamine and compounds having a condensed aromatic ring. The fluorescentdopant emitting blue light is added in an amount of 0.1 to 20% byweight. It is preferable that the ionization energy of the fluorescentdopant emitting blue light is smaller than the ionization energy of themain components so that the property for charge injection is improved.

The layer of a light emitting medium described above may comprise a holetransporting material or a hole injecting material.

The layer of a light emitting medium described above may comprise a holetransporting layer or a hole injecting layer.

The layer of a light emitting medium described above may comprise anelectron transporting material or an electron injecting material.

The layer of a light emitting medium described above may comprise anelectron transporting layer or an electron injecting layer.

It is preferable that the layer of a light emitting medium contactingthe anode contains an oxidizing agent. As the oxidizing agent containedin the layer of a light emitting medium, an oxidizing agent having theelectron-accepting property or an electron acceptor is preferable.Preferable examples of the oxidizing agent include Lewis acids, varioustypes of quinone derivatives, dicyanoquinodimethane derivatives andsalts formed from aromatic amines and Lewis acids. Preferable examplesof the Lewis acid include iron chloride, antimony chloride and aluminumchloride.

It is preferable that the organic light emitting medium contacting thecathode contains a reducing agent. Preferable examples of the reducingagent include alkali metals, alkaline earth metals, alkali metal oxides,alkaline earth metal oxides, oxides of rare earth elements, alkali metalhalides, alkaline earth metal halides, halides of rare earth elementsand complex compounds formed from alkali metals and aromatic compounds.Preferable examples of the alkali metal include Cs, Li, Na and K.

A layer of an inorganic compound may be disposed between at least one ofthe electrodes and the layer of a light emitting medium. Preferableexamples of the inorganic compound used in the layer of an inorganiccompound include various types of oxides, nitrides and oxide nitridessuch as alkali metal oxides, alkaline earth metal oxides, oxides of rareearth elements, alkali metal halides, alkaline earth metal halides,halides of rare earth elements, SIO_(x), AlO_(x), SiN_(x), SiON, AlON,GeO_(x), LiO_(x), LiON, TiO_(x), TiON, TaO_(x), TaON, TaN_(x) and C. Inparticular, as the component of the layer contacting the anode, SiO_(x),AlO_(x), SiN_(x), SiON, AlON, GeO_(x) and C are preferable since astable interface layer for injection is formed. As the component of thelayer contacting the cathode, LiF, MgF₂, CaF₂ and NaF are preferable.

Examples of the fluorescent compound having at least one structureselected form the fluoranthene skeleton structure and the peryleneskeleton structure, which is used in the present invention, includecompounds represented by general formulae [1′], [2′] and [1] to [18]shown in the following.X=Z=Y   [1′]X═W   [2′]

In the above formulae, Z represents a tetravalent group represented byany of the following general formulae (1) to (6):

X and Y each independently represent a divalent group represented by anyof the following general formulae (7) to (10):

and

-   -   W represents a divalent group represented by any of the        following general formulae (11) to (13):

In the above general formulae (1) to (13), R⁰ to R⁹⁹ each independentlyrepresent hydrogen atom, a halogen atom, cyano group, a substituted orunsubstituted alkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted cycloalkyl group having 6 to 10 carbon atoms, asubstituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, asubstituted or unsubstituted amino group having 1 to 30 carbon atoms, asubstituted or unsubstituted aryloxy group having 6 to 20 carbon atoms,a substituted or unsubstituted alkoxycarbonyl group having 1 to 20carbon atoms, a substituted or unsubstituted aralkyl group having 6 to30 carbon atoms, a substituted or unsubstituted aromatic hydrocarbongroup having 6 to 30 carbon atoms or a substituted or unsubstitutedheterocyclic group having 5 to 30 carbon atoms, and adjacent groupsrepresented by R⁰ to R⁹⁹ may be bonded to each other to form a cyclicstructure.

In the above general formulae [1] to [16], X¹ to X²⁰ each independentlyrepresent hydrogen atom, a linear, branched or cyclic alkyl group having1 to 20 carbon atoms, a linear, branched or cyclic alkoxy group having 1to 20 carbon atoms, a substituted or unsubstituted aryl group having 6to 30 carbon atoms, a substituted or unsubstituted aryloxy group having6 to 30 carbon atoms, a substituted or unsubstituted arylamino grouphaving 6 to 30 carbon atoms, a substituted or unsubstituted alkylaminogroup having 1 to 30 carbon atoms, a substituted or unsubstitutedarylalkylamino group having 7 to 30 carbon atoms or a substituted orunsubstituted alkenyl group having 8 to 30 carbon atoms, adjacentsubstituents and adjacent groups represented by X¹ to X²⁰ may be bondedto each other to form a cyclic structure, and, when the adjacentsubstituents are aromatic groups, the substituents may the same group.

It is preferable that the compounds represented by general formulae [1]to [16] have an amino group or an alkenyl group.

In the above general formulae [17] and [18], R¹ to R⁴ each independentlyrepresent an alkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted aryl group having 6 to 30 carbon atoms, any of a pair ofgroups represented by R¹ and R² and a pair of groups represented by R³and R⁴ may be bonded to each other through a carbon-carbon bond, —0— or—S—, R⁵ to R¹⁶ each independently represent hydrogen atom, a linear,branched or cyclic alkyl group having 1 to 20 carbon atoms, a linear,branched or cyclic alkoxy group having 1 to 20 carbon atoms, asubstituted or unsubstituted aryl group having 6 to 30 carbon atoms, asubstituted or unsubstituted aryloxy group having 6 to 30 carbon atoms,a substituted or unsubstituted arylamino group having 6 to 30 carbonatoms, a substituted or unsubstituted alkylamino group having 1 to 30carbon atoms, a substituted or unsubstituted arylalkylamino group having7 to 30 carbon atoms or a substituted or unsubstituted alkenyl grouphaving 8 to 30 carbon atoms, and adjacent substituents and adjacentgroups represented by R⁵ to R¹⁶ may be bonded to each other to form acyclic structure. It is preferable that at least one of the substituentsrepresented by R⁵ to R¹⁶ in the above general formulae has an amine oran alkenyl group.

Examples of the fluorescent compound having at least one pentaceneskeleton structure, which is used in the present invention, includecompounds represented by formulae [19] and [20] shown in the following.

In the above general formula [19], R¹ to R¹⁴ each independentlyrepresents hydrogen atom, an alkyl group having 1 to 10 carbon atoms, anaryloxy group having 6 to 20 carbon atoms, an arylalkyl group having 6to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, anarylamino group having 6 to 30 carbon atoms, an alkylamino group having2 to 20 carbon atoms or an arylalkylamino group having 6 to 30 carbonatoms, the groups represented by R¹ to R¹⁴ may be substituted, and atleast one pair of groups represented by R¹ to R¹⁴ which are adjacent toeach other are not hydrogen atom and form a cyclic structure.

In the above general formula [20], R¹⁵ to R²⁶ each independentlyrepresent hydrogen atom, an alkyl group having 1 to 10 carbon atoms, anaryloxy group having 6 to 20 carbon atoms, an arylalkyl group having 6to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, anarylamino group having 6 to 30 carbon atoms, an alkylamino group having2 to 20 carbon atoms or an arylalkylamino group having 6 to 30 carbonatoms, the groups represented by R¹⁵ to R²⁶ may be substituted, at leastone pair of groups represented by R¹⁵ to R²⁶ which are adjacent to eachother are not hydrogen atom and form a cyclic structure, and Ar¹ and Ar²each represent a substituted or unsubstituted aryl group having 6 to 30carbon atoms or a substituted or unsubstituted heterocyclic group having5 to 30 carbon atoms.

It is preferable that the fluorescent compound having the fluorantheneskeleton structure or the perylene skeleton structure has anelectron-donating group so that a high efficiency and a long life areachieved. As the electron-donating group, substituted and unsubstitutedarylamino groups are preferable.

It is preferable that the fluorescent compound having the fluorantheneskeleton structure, the perylene skeleton structure or the pentaceneskeleton structure has 5 or more condensed rings and more preferably 6or more condensed rings since the fluorescent compound having thisstructure has the peak wavelength of fluorescence at 540 to 650 nm andthe light emitted from the light emitting material emitting blue lightand the light emitted from the fluorescent compound are combined so asto emit white light.

It is preferable that the fluorescent compound has a plurality of thefluoranthene skeleton structures or a plurality of the perylene skeletonstructure since the emitted light is in the region of yellow to red. Itis more preferable that the fluorescent compound has anelectron-donating group and the fluoranthene skeleton structure or theperylene skeleton structure and has the peak wavelength of fluorescenceat 540 to 650 nm.

It is preferable that the light emitting material emitting blue lightused in the present invention is a styryl derivative, an anthracenederivative or an aromatic amine.

It is preferable that the styryl derivative described above is at leastone compound selected from distyryl derivatives, tristyryl derivatives,tetrastyryl derivatives and styrylamine derivatives.

It is preferable that the anthracene derivative described above is acompound having the phenylanthracene skeleton structure.

It is preferable that the aromatic amine described above is a compoundhaving 2 to 4 nitrogen atoms which are substituted with an aromaticgroup and more preferably a compound having 2 to 4 nitrogen atoms whichare substituted with an aromatic group and having at least one alkenylgroup.

Examples of the styryl derivative and the anthracene derivativedescribed above include compounds represented by general formulae [i] to[v] shown bellow. Examples of the aromatic amine described above includecompounds represented by general formulae [vi] and [vii] shown below.

In the above general formula, R^(1′) to R^(10′) each independentlyrepresent hydrogen atom, a halogen atom, cyano group, nitro group, asubstituted or unsubstituted alkyl group having 1 to 20 carbon atoms, asubstituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, asubstituted or unsubstituted aryloxy group having 6 to 30 groups, asubstituted or unsubstituted alkylthio group having 1 to 20 carbonatoms, a substituted or unsubstituted arylthio group having 6 to 30carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to30 carbon atoms, an unsubstituted single ring group having 5 to 30carbon atoms, a substituted or unsubstituted condensed multi-ring grouphaving 10 to 30 carbon atoms or a substituted or unsubstitutedheterocyclic group having 5 to 30 carbon atoms.

Ar¹ and Ar² each independently represent a substituted or unsubstitutedaryl group having 6 to 30 carbon atoms or a substituted or unsubstitutedalkenyl group. The substituent in the above groups is a substituted orunsubstituted alkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted alkoxy groups having 1 to 20 carbon atoms, a substitutedor unsubstituted aryloxy group having 6 to 30 carbon atoms, asubstituted or unsubstituted alkylthio group having 1 to 20 carbonatoms, a substituted or unsubstituted arylthio group having 6 to 30carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to30 carbon atoms, an unsubstituted single ring group having 5 to 30carbon atoms, a substituted or unsubstituted condensed multi-ring grouphaving 10 to 30 carbon atoms or a substituted or unsubstitutedheterocyclic group having 5 to 30 carbon atoms.

In the above general formula, R^(1′) to R^(10′) each independentlyrepresent hydrogen atom, a halogen atom, cyano group, nitro group, asubstituted or unsubstituted alkyl group having 1 to 20 carbon atoms, asubstituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, asubstituted or unsubstituted aryloxy group having 6 to 30 groups, asubstituted or unsubstituted alkylthio group having 1 to 20 carbonatoms, a substituted or unsubstituted arylthio group having 6 to 30carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to30 carbon atoms, an unsubstituted single ring group having 5 to 30carbon atoms, a substituted or unsubstituted condensed multi-ring grouphaving 10 to 30 carbon atoms or a substituted or unsubstitutedheterocyclic group having 5 to 30 carbon atoms.

Ar³ and Ar⁴ each independently represent a substituted or unsubstitutedaryl group having 6 to 30 carbon atoms or a substituted or unsubstitutedalkenyl group. The substituent in the above groups is a substituted orunsubstituted alkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted alkoxy groups having 1 to 20 carbon atoms, a substitutedor unsubstituted aryloxy group having 6 to 30 carbon atoms, asubstituted or unsubstituted alkylthio group having 1 to 20 carbonatoms, a substituted or unsubstituted arylthio group having 6 to 30carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to30 carbon atoms, an unsubstituted single ring group having 5 to 30carbon atoms, a substituted or unsubstituted condensed multi-ring grouphaving 10 to 30 carbon atoms, a substituted or unsubstitutedheterocyclic group having 5 to 30 carbon atoms or a substituted orunsubstituted alkenyl group having 4 to 40 carbon atoms.

n represents a number of 1 to 3, m represents a number of 1 to 3 andn+m≧2.

In the above general formula [ii], R^(1′) to R^(8′) each independentlyrepresent hydrogen atom, a halogen atom, cyano group, nitro group, asubstituted or unsubstituted alkyl group having 1 to 20 carbon atoms, asubstituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, asubstituted or unsubstituted aryloxy group having 6 to 30 groups, asubstituted or unsubstituted alkylthio group having 1 to 20 carbonatoms, a substituted or unsubstituted arylthio group having 6 to 30carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to30 carbon atoms, an unsubstituted single ring group having 5 to 30carbon atoms, a substituted or unsubstituted condensed multi-ring grouphaving 10 to 30 carbon atoms or a substituted or unsubstitutedheterocyclic group having 5 to 30 carbon atoms.

Ar³ and Ar⁴ each independently represent a substituted or unsubstitutedaryl group having 6 to 30 carbon atoms or a substituted or unsubstitutedalkenyl group. The substituent in the above groups is a substituted orunsubstituted alkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted alkoxy groups having 1 to 20 carbon atoms, a substitutedor unsubstituted aryloxy group having 6 to 30 carbon atoms, asubstituted or unsubstituted alkylthio group having 1 to 20 carbonatoms, a substituted or unsubstituted arylthio group having 6 to 30carbon atoms, a substituted or unsubstituted arylalkyl group having 6 to30 carbon atoms, an unsubstituted single ring group having 5 to 30carbon atoms, a substituted or unsubstituted condensed multi-ring grouphaving 10 to 30 carbon atoms, a substituted or unsubstitutedheterocyclic group having 5 to 30 carbon atoms or a substituted orunsubstituted alkenyl group having 4 to 40 carbon atoms.

In the above general formula, R^(1″) to R^(10″) each independentlyrepresent hydrogen atom, an alkenyl group, an alkyl group, a cycloalkylgroup, an aryl group which may be substituted, an alkoxy group, anaryloxy group, an alkylamino group, an arylamino group or a heterocyclicgroup which may be substituted. a and b each represent an integer of 1to 5 and, when any of a and b represents an integer of 2 or greater, aplurality of R^(1″) or R^(2″) may represent the same or differentgroups, a plurality of groups represented by R^(1″) or R^(2″) may bebonded to each other to form a ring, and a pair of groups represented byR^(3″) and R^(4″), R^(5″) and R^(6″), R^(7″) and R^(8″) or R^(9″) andR^(10″) may form a ring via the bonding within the pair. L¹ represents asingle bond, —O—, —S—, —N(R)—, R representing an alkyl group or an arylgroup which may be substituted, or an arylene group.

In the above general formula, R^(11″) to R^(20″) each independentlyrepresent hydrogen atom, an alkenyl group, an alkyl group, a cycloalkylgroup, an aryl group, an alkoxy group, an aryloxy group, an alkylaminogroup, an arylamino group or a heterocyclic group which may besubstituted. c, d, e and f each represent an integer of 1 to 5 and, whenany of c, d, e and f represents an integer of 2 or greater, a pluralityof R^(11″), R^(12″), R^(16″) or R^(17″) may represent the same ordifferent groups, a plurality of groups represented by R^(11″), R^(12″),R^(16″) or R^(17″) may be bonded to each other to form a ring and a pairof groups represented by R^(13″) and R^(14″) or R^(18″) and R^(19″) mayform a ring via the bonding within the pair. L² represents a singlebond, —O—, —S—, —N(R)—, R representing an alkyl group or an aryl groupwhich may be substituted, or an arylene group.

In the above general formula, Ar^(3′), Ar^(4′) and Ar^(5′) eachindependently represent a substituted or unsubstituted monovalentaromatic group having 6 to 40 carbon atoms, at least one of the groupsrepresented by Ar^(3′) to Ar^(5′) may have a styryl group and grepresents an integer of 1 to 4.

In the above general formula, Ar^(6′), Ar^(7′) Ar^(9′), Ar^(11′) andAr^(12′) each independently represent a substituted or unsubstitutedmonovalent aromatic group having 6 to 40 carbon atoms, Ar^(8′) andAr^(10′) each independently represent a substituted or unsubstituteddivalent aromatic group having 6 to 40 carbon atoms, at least one of thegroups represented by Ar^(6′) to Ar^(12′) may have styryl group orstyrylene group and h and k each represent an integer of 0 to 2.

It is preferable that the above fluorescent dopant emitting blue lightis at least one compound selected from styrylamines, styryl compoundssubstituted with an amine and compounds having a condensed aromaticring.

Examples of the above styrylamine and the above styryl compoundsubstituted with an amine include compounds represented by generalformulae [viii] and [ix] shown below. Examples of the above compoundhaving a condensed aromatic ring include compounds represented bygeneral formula [x] shown below.

In the above general formula, Ar^(1″), Ar^(2″) and Ar^(3″) eachindependently represent a substituted or unsubstituted arylene grouphaving 6 to 40 carbon atoms, at least one of the groups represented byAr^(1″) to Ar^(3″) has styryl group and p represents an integer of 1 to3.

In the above general formula, Ar^(4″) and Ar^(5″) each independentlyrepresent an arylene group having 6 to 30 carbon atoms, E¹ and E² eachindependently represent an aryl group having 6 to 30 carbon atoms, analkyl group, hydrogen atom or cyano group, q represents an integer of 1to 3 and at least one of U and V represents a substituent having anamino group. It is preferable that the amino group is an arylaminogroup.(A_(r)B   [x]

In the above general formula, A represents an alkyl group or an alkoxygroup having 1 to 16 carbon atoms, a substituted or unsubstituted arylgroup having 6 to 30 carbon atoms, a substituted or unsubstitutedalkylamino group having 6 to 30 carbon atoms or a substituted orunsubstituted arylamino group having 6 to 30 carbon atoms, B representsa condensed aromatic ring group having 10 to 40 carbon atoms and rrepresents an integer of 1 to 4.

The present invention will be described more specifically with referenceto examples in the following. However, the present invention is notlimited to the examples.

EXAMPLE 1 Preparation of an Organic EL Device (An Example of the FirstConstruction: the Fluoranthene Skeleton Structure)

A glass substrate of 25 mm×75 mm×1.1 mm thickness having a transparentelectrode line of ITO (In—Sn—O) (manufactured by GEOMATEC Company) wascleaned with isopropyl alcohol for 5 minutes under application ofultrasonic wave and treated by the UV ozone cleaning for 30 minutes. Thecleaned glass substrate having a transparent electrode line was attachedto a substrate holder in a vacuum vapor deposition apparatus. On theface of the substrate on which the transparent electrode line wasdisposed, a film ofN,N′-bis(N,N′-diphenyl-4-aminphenyl)-N,N-diphenyl-4,4′-diamino-1,1′-biphenyl(a TPD232 film) having a thickness of 60 nm was formed in a manner suchthat the film covered the transparent electrode line. The TPD232 filmworked as the hole injecting layer. Then, a film of4,4′-bis[N-(l-naphthyl)-N-phenylamino]biphenyl (an NPD film) having athickness of 20 nm was formed on the TPD232 film. The NPD film worked asthe hole transporting layer. On the NPD film, a styryl derivative DPVBihaving the structure shown below and a fluorescent compound El havingthe structure also shown below (the peak wavelength of fluorescence: 565nm) were vapor deposited in amounts such that the ratio of the amountsby weight was 40:0.04 and a film having a thickness of 40 nm was formed.This film worked as the light emitting layer emitting white light. Onthe film formed above, a film of tris(8-quinolinol)aluminum (an Alqfilm) having a thickness of 20 nm was formed. The Alq film worked as theelectron injecting layer. Subsequently, Li (lithium, manufactured bySAES GETTERS Company) and Alq were binary vapor deposited and an Alq:Lifilm was formed as the electron injecting layer (a cathode). On theformed Alq:Li film, aluminum metal was vapor deposited and a metalcathode was formed. Thus, an organic EL device was formed.

The properties of the obtained organic EL device were evaluated. Adirect voltage of 5 V was applied in a condition such that the ITO anodewas connected to the positive electrode (+) and the aluminum cathode wasconnected to the negative electrode (−). White light was emitted at aluminance of 181 cd/m², a maximum luminance of 110,000 cd/m² and anefficiency of light emission of 8.8 cd/A. The chromaticity coordinateswere (0.36, 0.32) and emission of white light could be confirmed. Thelife was as long as 1,800 hours when the device was driven under aconstant current driving at an initial luminance of 1,000 cd/m².

EXAMPLE 2 Preparation of an Organic EL Device (An Example of the SecondConstruction: the Fluoranthene Skeleton Structure)

A glass substrate of 25 mm×75 mm×1.1 mm thickness having a transparentelectrode line of ITO (In—Sn—O) (manufactured by GEOMATEC Company) wascleaned with isopropyl alcohol for 5 minutes under application ofultrasonic wave and treated by the UV ozone cleaning for 30 minutes. Thecleaned glass substrate having a transparent electrode line was attachedto a substrate holder in a vacuum vapor deposition apparatus. On theface of the substrate on which the transparent electrode line wasdisposed, a TPD232 film having a thickness of 60 nm was formed in amanner such that the film covered the transparent electrode line. TheTPD232 film worked as the hole injecting layer. Then, an NPD film havinga thickness of 20 nm was formed on the TPD232 film. When the NPD filmwas formed, the fluorescent compound described above (E1) was added inan amount such that the amounts by weight of NPD to E1 was 20:0.1. TheNPD film worked as the light emitting layer emitting yellowish orangelight and having the hole transporting property. On the NPD film, a filmof DPVBi having a thickness of 40 nm was formed as the light emittinglayer emitting blue light. On the film formed above, an Alq film havinga thickness of 20 nm was formed. The Alq film worked as the electroninjecting layer. Subsequently, Li (lithium, manufactured by SAES GETTERSCompany) and Alq were binary vapor deposited and an Alq:Li film wasformed as the electron injecting layer (a cathode). On the formed Alq:Lifilm, aluminum metal was vapor deposited and a metal cathode was formed.Thus, an organic EL device was formed.

The properties of the obtained organic EL device were evaluated. Adirect voltage of 5 V was applied in a condition such that the ITO anodewas connected to the positive electrode (+) and the aluminum cathode wasconnected to the negative electrode (−). White light was emitted at aluminance of 151 cd/m², a maximum luminance of 80,000 cd/m² and anefficiency of light emission of 6.8 cd/A. The life was as long as 1,100hours when the device was driven under a constant voltage at an initialluminance of 1,000 cd/m².

EXAMPLE 3 Preparation of an Organic EL Device (An Example of the ThirdConstruction: the Fluoranthene Skeleton Structure)

A glass substrate of 25 mm×75 mm×1.1 mm thickness having a transparentelectrode line of ITO (In—Sn—O) (manufactured by GEOMATEC Company) wascleaned with isopropyl alcohol for 5 minutes under application ofultrasonic wave and treated by the UV ozone cleaning for 30 minutes. Thecleaned glass substrate having a transparent electrode line was attachedto a substrate holder in a vacuum vapor deposition apparatus. On theface of the substrate on which the transparent electrode line wasdisposed, a TPD232 film having a thickness of 60 nm was formed in amanner such that the film covered the transparent electrode line. TheTPD232 film worked as the hole injecting layer. Then, an NPD film havinga thickness of 20 nm was formed on the TPD232 film. The NPD film workedas the hole transporting layer. On the NPD film, the fluorescentcompound (El) described above was vapor deposited and a film having athickness of 3 nm was formed. This film worked as the layer of afluorescent compound and emitted orange light. On the thus formed film,a styryl derivative DPVBi was vapor deposited and a film. having athickness of 40 nm was formed. This film worked as the light emittinglayer emitting blue light. On the film formed above, an Alq film havinga thickness of 20 nm was formed. The Alq film worked as the electroninjecting layer. Subsequently, Li (lithium, manufactured by SAES GETTERSCompany) and Alq were binary vapor deposited and an Alq:Li film wasformed as the electron injecting layer (a cathode). On the formed Alq:Lifilm, aluminum metal was vapor deposited and a metal cathode was formed.Thus, an organic EL device was formed.

The properties of the obtained organic EL device were evaluated. Adirect voltage of 5 V was applied in a condition such that the ITO anodewas connected to the positive electrode (+) and the aluminum cathode wasconnected to the negative electrode (−). White light was emitted at aluminance of 131 cd/m², a maximum luminance of 60,000 cd/m² and anefficiency of light emission of 5.8 cd/A. The life was as long as 1,400hours when the device was driven under a constant voltage at an initialluminance of 1,000 cd/m².

EXAMPLE 4 Preparation of an Organic EL Device (An Example of Adding aHole Transporting Material to the Light Emitting Layer)

A glass substrate of 25 mm×75 mm×1.1 mm thickness having a transparentelectrode line of ITO (In—Sn—O) (manufactured by GEOMATEC Company) wascleaned with isopropyl alcohol for 5 minutes under application ofultrasonic wave and treated by the UV ozone cleaning for 30 minutes. Thecleaned glass substrate having a transparent electrode line was attachedto a substrate holder in a vacuum vapor deposition apparatus. On theface of the substrate on which the transparent electrode line wasdisposed, a TPD232 film having a thickness of 60 nm was formed in amanner such that the film covered the transparent electrode line. TheTPD232 film worked as the hole injecting layer. Then, an NPD film havinga thickness of 20 nm was formed on the TPD232 film. The NPD film workedas the hole transporting layer. On the NPD film, the fluorescentcompound described above (El), NPD as the hole transporting material anda styryl derivative DPVBi as the material emitting blue light were mixedin amounts such that the ratio of the amounts by weight was 20:20:0.04and a film was formed from the mixture. This film worked as the lightemitting layer emitting white light. On the film formed above, an Alqfilm having a thickness of 20 nm was formed. The Alq film worked as theelectron injecting layer. Subsequently, Li (lithium, manufactured bySAES GETTERS Company) and Alq were binary vapor deposited and an Alq:Lifilm was formed as the electron injecting layer (a cathode). On theformed Alq:Li film, aluminum metal was vapor deposited and a metalcathode was formed. Thus, an organic EL device was formed.

The properties of the obtained organic EL device were evaluated. Adirect voltage of 5 V was applied in a condition such that the ITO anodewas connected to the positive electrode (+) and the aluminum cathode wasconnected to the negative electrode (−). White light was emitted at aluminance of 131 cd/m², a maximum luminance of 120,000 cd/m² and anefficiency of light emission of 8.0 cd/A. The life was as long as 2,000hours when the device was driven under a constant voltage at an initialluminance of 1,000 cd/M².

EXAMPLE 5 Preparation of an Organic EL Device (An Example of the FirstConstruction: the Pentacene Skeleton Structure)

An organic EL device was prepared in accordance with the same proceduresas those conducted in Example 1 except that a styryl derivative DPVBi,PAVB having the structure shown below as the fluorescent dopant emittingblue light and a fluorescent compound F1 having the structure shownbelow (the peak wavelength of fluorescence: 595 nm) were vapor depositedon the NPD film in amounts such that the ratio of the amounts by weightwas 40:1:0.05 and a film having a thickness of 40 nm was formed.

The properties of the obtained organic EL device were evaluated. Adirect voltage of 6 V was applied in a condition such that the ITO anodewas connected to the positive electrode (+) and the aluminum cathode wasconnected to the negative electrode (−). White light was emitted at aluminance of 319 cd/m², a maximum luminance of 100,000 cd/m² and anefficiency of light emission of 7.28 cd/A. The chromaticity coordinateswere (0.33, 0.34) and emission of white light could be confirmed. Thelife was as long as 3,500 hours when the device was driven under aconstant voltage at an initial luminance of 1,000 cd/m².

EXAMPLE 6 Preparation of an Organic EL Device (An Example of the SecondConstruction: the Pentacene Skeleton Structure)

A glass substrate of 25 mm×75 mm×1.1 mm thickness having a transparentelectrode line of ITO (In—Sn—O) (manufactured by GEOMATEC Company) wascleaned with isopropyl alcohol for 5 minutes under application ofultrasonic wave and treated by the UV ozone cleaning for 30 minutes. Thecleaned glass substrate having a transparent electrode line was attachedto a substrate holder in a vacuum vapor deposition apparatus. On theface of the substrate on which the transparent electrode line wasdisposed, a TPD232 film having a thickness of 60 nm was formed in amanner such that the film covered the transparent electrode line. TheTPD232 film worked as the hole injecting layer. Then, an NPD film havinga thickness of 20 nm was formed on the TPD232 film. On the NPD film, astyryl derivative DPVBi and a fluorescent compound (Fl) were vapordeposited in amounts such that the ratio of the amounts by weight was2:0.026 and a film having a thickness of 2 nm was formed. This filmworked as the light emitting layer emitting orange light. On the formedfilm, the styryl derivative DPVBi and PAVB as the fluorescent dopantemitting blue light were vapor deposited in amount such that the ratioof the amount by weight was 38:1 and a film having a thickness of 38 nmwas formed. This film worked as the light emitting layer emitting bluelight. On the film formed above, an Alq film having a thickness of 20 nmwas formed. The Alq film worked as the electron injecting layer.Subsequently, Li (lithium, manufactured by SAES GETTERS Company) and Alqwere binary vapor deposited and an Alq:Li film was formed as theelectron injecting layer (a cathode). On the formed Alq:Li film,aluminum metal was vapor deposited and a metal cathode was formed. Thus,an organic EL device was formed.

The properties of the obtained organic EL device were evaluated. Adirect voltage of 5.5 V was applied in a condition such that the ITOanode was connected to the positive electrode (+) and the aluminumcathode was connected to the negative electrode (−). White light wasemitted at a luminance of 233 cd/m², a maximum luminance of 80,000 cd/m²and an efficiency of light emission of 6.85 cd/A. The life was as longas 2,100 hours when the device was driven under a constant voltage at aninitial luminance of 1,000 cd/m².

COMPARATIVE EXAMPLE 1

An organic EL device was prepared in accordance with the same proceduresas those conducted in Example 1 except that rubrene which is generallyused as a fluorescent compound emitting orange light was used in placeof the fluorescent compound (E1).

The properties of the obtained organic EL device were evaluated. Adirect voltage of 6 V was applied in a condition such that the ITO anodewas connected to the positive electrode (+) and the aluminum cathode wasconnected to the negative electrode (−). White light was emitted at aluminance of 140 cd/m², a maximum luminance of 60,000 cd/m² and anefficiency of light emission of 4.0 cd/A. The efficiency of lightemission was markedly inferior to those obtained in Examples. The lifewas as short as 560 hours when the device was driven under a constantvoltage at an initial luminance of 1,000 cd/m².

Industrial Applicability

As described above in detail, the organic EL device of the presentinvention emits white light and has an efficiency of light emission ashigh as 5 lumen/W or greater and 5 cd/A or greater and a life as long as10,000 hours or longer under the condition of ordinary use. Thus, theorganic EL device exhibits properties sufficient for practicalapplications. The organic EL device is advantageously used as the lightemitting device in various types of display apparatuses.

1. An organic electroluminescence device which comprises a pair ofelectrodes and a layer of a light emitting medium disposed between thepair of electrodes, wherein the layer of a light emitting mediumcomprises a material emitting blue light and a fluorescent compoundhaving a perylene skeleton structure, wherein the fluorescent compoundhas a peak wavelength of fluorescence at 540 nm or more.
 2. An organicelectroluminescence device according to claim 1, wherein the layer of alight emitting medium comprises a light emitting layer A comprising thematerial emitting blue light and the fluorescent compound.
 3. An organicelectroluminescence device according to claim 1, wherein the layer of alight emitting medium comprises a light emitting layer emitting bluelight and a light emitting layer A which comprises the material emittingblue light and the fluorescent compound.
 4. An organicelectroluminescence device according to claim 1, wherein the layer of alight emitting medium comprises a light emitting layer B comprising thematerial emitting blue light and a layer comprising the fluorescentcompound.
 5. (Canceled).
 6. An organic electroluminescence deviceaccording to claim 2, wherein light emitting layer A further comprises afluorescent dopant emitting blue light.
 7. An organicelectroluminescence device according to claim 3, wherein light emittinglayer A further comprises a fluorescent dopant emitting blue light. 8.An organic electroluminescence device according to claim 4, whereinlight emitting layer B further comprises a fluorescent dopant emittingblue light.
 9. An organic electroluminescence device according to claim3, wherein the light emitting layer emitting blue light furthercomprises a fluorescent dopant emitting blue light.
 10. (Canceled). 11.An organic electroluminescence device according to claim 1, wherein thelayer of a light emitting medium comprises a hole transporting materialor a hole injecting material.
 12. An organic electroluminescence deviceaccording to claim 1, wherein the layer of a light emitting mediumcomprises a hole transporting layer or a hole injecting layer.
 13. Anorganic electroluminescence device according to claim 1, wherein thelayer of a light emitting medium comprises an electron transportingmaterial or an electron injecting material.
 14. An organicelectroluminescence device emitting according to claim 1, wherein thelayer of a light emitting medium comprises an electron transportinglayer or an electron injecting layer.
 15. An organic electroluminescencedevice according to claim 1, wherein the layer of a light emittingmedium contacts an anode and comprises an oxidizing agent.
 16. Anorganic electroluminescence device according to claim 1, wherein thelayer of a light emitting medium contacts a cathode and comprises areducing agent.
 17. An organic electroluminescence device according toclaim 1, wherein a layer of an inorganic compound is disposed between atleast one of the electrodes and the layer of a light emitting medium.18. An organic electroluminescence device according to claim 1, whereinthe light emitting material emitting blue light is a styryl derivative,an anthracene derivative or an aromatic amine.
 19. An organicelectroluminescence device according to claim 18, wherein the styrylderivative is at least one compound selected from distyryl derivatives,tristyryl derivatives, tetrastyryl derivatives and styrylaminederivatives.
 20. An organic electroluminescence device according toclaim 18, wherein the anthracene derivative is a compound having aphenylanthracene skeleton structure.
 21. An organic electroluminescencedevice according to claim 18, wherein the aromatic amine is a compoundhaving 2 to 4 nitrogen atoms which are substituted with an aromaticgroup.
 22. An organic electroluminescence device according to claim 18,wherein the aromatic amine is a compound having 2 to 4 nitrogen atomswhich are substituted with an aromatic group and having at least onealkenyl group.
 23. An organic electroluminescence device according toclaim 6, wherein the fluorescent dopant emitting blue light is at leastone compound selected from styrylamines, styryl compounds substitutedwith an amine and compounds having a condensed aromatic ring.
 24. Anorganic electroluminescence device according to claim 7, wherein thefluorescent dopant emitting blue light is at least one compound selectedfrom styrylamines, styryl compounds substituted with an amine andcompounds having a condensed aromatic ring.
 25. An organicelectroluminescence device according to claim 8, wherein the fluorescentdopant emitting blue light is at least one compound selected fromstyrylamines, styryl compounds substituted with an amine and compoundshaving a condensed aromatic ring.
 26. An organic electroluminescencedevice according to claim 9, wherein the fluorescent dopant emittingblue light is at least one compound selected from styrylamines, styrylcompounds substituted with an amine and compounds having a condensedaromatic ring.
 27. An organic electroluminescence device according toclaim 10, wherein the fluorescent dopant emitting blue light is at leastone compound selected from styrylamines, styryl compounds substitutedwith an amine and compounds having a condensed aromatic ring.
 28. Anorganic electroluminescence device according to claim 1, wherein thefluorescent compound has an electron-donating group.
 29. An organicelectroluminescence device according to claim 1, wherein the fluorescentcompound has a peak wavelength of fluorescence at 540 to 650 nm.
 30. Anorganic electroluminescence device according to claim 1, which emitswhite light.